In general, a piezoelectric valve is a device that opens or closes a fluid line using a piezoelectric element bending by voltage. In recent years, the piezoelectric valve has been installed in cars and controls the flow of fuel supplied to an engine of the car or controls the flow of air supplied to an airbag mounted in the back of a seat of the car.
FIG. 1 is a sectional view illustrating the construction of a conventional piezoelectric valve. As shown in the drawing, the conventional piezoelectric valve is configured such that a first end of a plate-shaped piezoelectric element 7 installed in a casing 2 bends by voltage applied to the piezoelectric element 7 and opens or closes valve seats 4A and 5A of the casing 2. Here, the piezoelectric valve may be configured to open or close the opposite valve seats 4A and 5A of the casing 2 as shown in the drawing, or may be configured to open or close one valve seat 4A, 5A unlike the embodiment shown in the drawing.
The above-mentioned conventional piezoelectric valve may be configured in such a way that a second end of the piezoelectric element 7 is fastened to the casing 2 using a rubber plate 8, as shown in the drawing, or unlike the embodiment shown in the drawing, the second end of the piezoelectric element 7 may be fastened to the casing 2 using a hardener such as an epoxy resin.
However, in the conventional piezoelectric valve, the second end of the piezoelectric element 7 is fastened to the casing 2 using the rubber plate 8 or using the hardener such as the epoxy resin, so the conventional piezoelectric valve is problematic in that it is difficult to fasten the piezoelectric element 7 to the casing 2. Further, due to the piezoelectric element fastening method using the rubber plate 8 or using the hardener, the fastened position of the piezoelectric element 7 is not adjustable, so the piezoelectric element 7 cannot control the flow rate of a fluid flowing into the valve seats 4A and 5A.
As a related art technology that can overcome the above-mentioned problems, a piezoelectric valve was proposed in Korean Patent No. 10-1155116 owned by the inventor of this invention.
As shown in FIG. 2, in the above-mentioned related art technology, a plate-shaped piezoelectric element 80 that opens or closes a valve unit 60 provided in a valve body 50 is fastened by a fastener in such a way that the fastened position of the piezoelectric element 80 is adjustable, so the flow rate of a fluid passing the valve unit 60 can be controlled by adjusting the fastened position of the piezoelectric element 80 using the fastener.
Described in detail, in the piezoelectric valve of the related art technology, the fastener is configured such that an insulation stick 91 is integrally fastened to the second end of the piezoelectric element 80 and is fitted over an adjustment bolt 93 with an elastic body 95 elastically supporting the insulation stick 91. Further, an adjustment nut 97 is engaged with the adjustment bolt 93. Here, to control the flow rate of a fluid passing the valve unit 60 of the piezoelectric valve, it is required to rotate the adjustment nut 97 so that the adjustment nut 97 compresses the insulation stick 91 and moves the second end of the piezoelectric element 80.
In other words, in the piezoelectric valve of the related art technology, the head of the adjustment bolt 93 is immovably embedded in the casing 52 while being covered with a cover 56 constituting the valve body 50, as shown in FIG. 2, so, to control the flow rate of a fluid passing the valve unit 60, it is required to rotate the adjustment nut 97 instead of rotating the adjustment bolt 93.
However, in the piezoelectric valve of the related art technology, the adjustment nut 97 is covered with another cover 54, so it is impossible to rotate the adjustment nut 97 after mounting the cover 54 to the casing 52. Accordingly, after mounting the cover 54 to the casing 52, it is impossible to rotate the adjustment nut 97 or to control the flow rate of a fluid passing the valve unit 60.
Described in detail, during a process of manufacturing the piezoelectric valve of the related art technology, a user controls the flow rate of a fluid passing the valve unit 60 by rotating the adjustment nut 97 after mounting both the valve unit 60 and the piezoelectric element 80 in the casing 52. After controlling the flow rate of the fluid, the two covers 54 and 56 are welded to their locations on the casing 52, so the manufacturing of the piezoelectric valve is finished. After manufacturing the piezoelectric valve, the manufactured valve is subjected to both an electric leakage test and a flow rate test for quality control.
However, the piezoelectric valve of the related art technology is problematic in that a flow deviation may be generated in the valve due to assembly tolerances of respective parts of the valve, for example, the covers 54 and 56 welded to the casing with different junction depths. Here, although a flow deviation is generated in the piezoelectric valve as described above, it is impossible to control the flow rate of the valve again because the adjustment nut 97 and the adjustment bolt 93 are covered with the respective covers 54 and 56, so the manufactured valve should be discarded resulting in large economic loss.